Polymer scale deposition preventive agent

ABSTRACT

A polymer scale deposition preventive agent for use in polymerization of a monomer having an ethylenically unsaturated double bond, comprising an alkaline solution containing a condensation product of (A) a diphenyl compound having at least two amino groups and (B) a quinone compound. When the aforementioned monomer is polymerized in a polymerization vessel having a coating formed by applying the aforementioned preventive agent to inner wall surfaces followed by drying, polymer scale can be effectively prevented from being deposited not only on the areas located in the liquid-phase region but also on the areas around the interface between the gas and liquid phases in the polymerization vessel. When an obtained polymer is formed into a sheet or the like, it is possible to obtain a formed product having few fish eyes and good initial coloration.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polymer scale deposition preventiveagent for use in polymerization of a monomer having an ethylenicallyunsaturated double bond, and a process for producing a polymer using thesame.

2. Description of the Prior Art

Heretofore, as methods for polymerization of a monomer having anethylenically unsaturated double bond have been known suspension,emulsion, solution, gas phase and bulk polymerization processes and thelike. In any of these polymerization processes, polymer scale is liableto be deposited on the areas with which the monomer comes into contact,such as inner walls, stirring equipment and so on of a polymerizationvessel.

The deposition of the polymer scale results in disadvantages that theyield of the polymer, cooling capacity of the polymerization vessel andso on are lowered, and that the polymer scale may peel off and mix intoa polymeric product, thereby consequently impairing the quality ofproducts obtained by forming such a polymeric product. In addition,removal of deposited polymer scale is necessarily very laborious andtime-consuming. Further, the polymer scale contains unreacted monomers,so that there is a risk of physical disorders in the human body due tomonomers, as having been a very serious problem in recent years.

In the prior art, for preventing such polymer scale deposition on thepolymerization vessel inner wall and so forth, for example, as locallypracticed in suspension polymerization of vinyl chloride, there havebeen known a method in which a polymer scale deposition preventive agentcomprising a polar organic compound such as amine compounds, quinonecompounds, aldehyde compounds and so on is applied to the polymerizationvessel inner wall to form a coating, and a method in which suchcompounds are added to an aqueous medium for performing suspensionpolymerization (Japanese Patent Publication (KOKOKU) No. 45-30343).

However, these methods have the disadvantage that, although the polymerscale deposition preventive effect is exhibited while polymerization isrepeated for up to about 5 or 6 batches, the preventive effectdiminishes if the number of repeated batches of polymerization exceedsthe above (that is, the durability is poor). This point exertsemphasized influence especially when a water-soluble catalyst is usedfor polymerization, resulting in unsatisfaction from an industrialviewpoint.

For overcoming the above disadvantage, for example, JapanesePre-examination Patent Publication (KOKAI) No. 53-13689 proposes amethod in which the inner wall, etc. of a polymerization vessel arecoated with a polymer scale deposition preventive agent comprising acondensation product of an aromatic amine compound as an effectiveconstituent. When such a polymer scale deposition preventive agent isapplied to the areas with which monomers comes into contact, such as theinner wall surface of a polymerization vessel and so on, and a coatingis thereby formed, then no polymer scale deposition takes place in theliquid-phase region in the polymerization vessel even afterpolymerization is repeatedly performed by about 100 to 200 batches.Besides, even in the aforementioned case where a water-soluble catalystis used, deposition of polymer scale in the liquid-phase region issimilarly prevented.

However, even after the coating of the polymer scale depositionpreventive agent comprising a condensation product of the aforementionedaromatic amine compound as its effective constituent is formed, therestill remains a drawback that polymer scale deposition occurs on theareas around the interface between the gas phase and the liquid phaselocated at an upper portion of the interior of the polymerizationvessel.

Once polymer scale deposition occurs on the areas around the interfacebetween the gas and liquid phases, the deposited polymer scale will growgradually as polymerization runs are repeated, and at last it may peeloff to be incorporated into the polymeric product. If the polymericproduct is mixed with the polymer scale in such a manner, when thepolymeric product is processed into formed products such as sheets orthe like, many fish eyes are generated in the obtained formed products,and the quality of the formed products is seriously deteriorated.

Besides, formed products, which are obtained when the polymeric productobtained by polymerization is formed into sheets or the like, arerequired to have a high whiteness. That is, even when a polymericproduct is formed into a sheet or the like without any addition ofcoloring agent, the resulting formed product may be more or lesscolored, and such coloration, called initial coloration, is desired tobe as slight as possible. However, when the coating of theaforementioned polymer scale deposition preventive agent comprising acondensation product of the aromatic amine compound as its effectiveconstituent is formed, the coating may peel off or dissolve to beincorporated into the polymeric product, so that whiteness of formedproducts may be deteriorated, that is, initial coloration may bedeteriorated.

SUMMARY OF THE INVENTION

Accordingly it is an object of the present invention to provide apolymer scale deposition preventive agent for use in polymerization of amonomer having an ethylenically unsaturated double bond that can preventeffectively the deposition of polymer scale, not only on the areas inthe liquid-phase region but also on the areas around the interfacebetween the gas and liquid phases inside a polymerization vessel, andthat makes it possible to produce a polymer capable of producing formedproducts having a very small number of fish eyes and good initialcoloration when formed into sheets or the like; and a process forproducing a polymer which utilizes the same.

The present invention provides, as means of achieving the above object,a polymer scale deposition preventive agent for use in polymerization ofa monomer having an ethylenically unsaturated double bond, comprising analkaline solution containing a condensation product of:

(A) a diphenyl compound having at least two amino groups represented bythe following general formula (1): ##STR1## wherein a plurality of R¹ 'smay be the same or different, which are --H, --OH, --COOH, --SO₃ H,--NH₂, --Cl, --NO₂, --COCH₃, --OCH₃, --N(CH₃)₂ or an alkyl group having1 to 3 carbon atoms, wherein X is an alkylene group having 1 to 5 carbonatoms, --N(CH₃)--, --C(CH₃)₂ --, --CONH--, --P(═O)H--, --SO₂ --, --O--,--S-- or --Si(R)₂ -- where R is an alkyl group having 1-10 carbon atoms,and wherein n is an integer of 1 or 2; and

(B) a quinone compound.

Further, the present invention provides a process for producing apolymer by polymerization of a monomer having an ethylenicallyunsaturated double bond in a polymerization vessel, comprising the stepof performing said polymerization in a polymerization vessel having acoating formed by drying after applying, on inner wall surfaces of thevessel, an alkaline solution containing a condensation product of:

(A) a diphenyl compound having at least two amino groups represented bythe following general formula (1): ##STR2## wherein a plurality of R¹ 'smay be the same or different, which are --H, --OH, --COOH, --SO₃ H,--NH₂, --Cl, --NO₂, --COCH₃, --OCH₃, --N(CH₃)₂ or an alkyl group having1 to 3 carbon atoms, wherein X is an alkylene group having 1 to 5 carbonatoms, --N(CH₃)--, --C(CH₃)₂ --, --CONH--, --P(═O)H--, --SO₂ --, --O--,--S-- or --Si(R)₂ -- where R is an alkyl group having 1-10 carbon atoms,and wherein n is an integer of 1 or 2; and

(B) a quinone compound; whereby polymer scale is prevented from beingdeposited in the polymerization vessel.

According to the present invention, deposition of polymer scale in apolymerization vessel can be effectively prevented, not only on theareas in the liquid phase region but also on the areas around theinterface between the gas phase and the liquid phase.

Therefore, where polymerization is conducted by applying the presentinvention, the operation of removing polymer scale need not be performedevery run of polymerization, and productivity is thereby improved.

In addition, the polymer obtained by polymerization with application ofthe present invention can be processed into formed products such assheets or the like which have very few fish eyes.

Furthermore, the aforementioned formed products have good initialcoloration. Specifically, the luminosity index (L value) in the Hunter'scolor difference equation described in JIS Z 8730 (1980) is, forexample, 70 or more in the case of vinyl chloride polymers, and 80 ormore in the case of SBR.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Component (A)

The component (A) is a diphenyl compound having at least two aminogroups (--NH₂) represented by the aforementioned general formula (1).

As the component (A) are specifically exemplified 4,4'-diaminodiphenylsulfide, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylpropane,4,4'-diaminodiphenylsulfone, bis(4-aminophenyl)diethylsilane,bis(4-aminophenyl)phosphine oxide, bis (4-aminophenyl) -N-methylamine,4,4'-diaminobenzanilide, 4,4'-diaminodiphenylmethane and the like.

Among them, preferred are 4,4'-diaminodiphenylsulfone,4,4'-diaminobenzanilide, 4,4'-diaminodiphenyl ether and4,4'-diaminodiphenylmethane.

The aforementioned component (A) can be used alone as one species, or incombination of two or more species.

Component (B)

As the quinone compound (B), for example, are exemplified benzoquinonecompounds represented by the following general formulae (2) and (3), andnaphthoquinone compounds represented by the following general formulae(4) and (5). ##STR3## wherein in each of the formulae (2) and (3), aplurality of R² 's may be the same or different, which are --H, --NH₂,--Cl, --Br, --OH, --NO₂, --COCH₃, --OCH₃, --N(CH₃)₂, --COOH, --SO₃ H, oran alkyl group having 1 to 3 carbon atoms.

As the benzoquinone compound represented by the aforementioned generalformulae (2) and (3) are specifically exemplified o- andp-benzoquinones, hydroxy-p-benzoquinone, chloro-p-benzoquinone,bromo-p-benzoquinone, duroquinone, chloranil and the like. ##STR4##wherein in each of the formulae (4) and (5), a plurality of R² 's may bethe same or different, which are as described above, and wherein aplurality of R³ 's may be the same or different, which are --H, --Cl,--Br, --OH, --COCH₃, --OCH₃, --CH₃, --COOH or --SO₃ H.

Specifically there are exemplified 6-methyl-1,4-naphthoquinone,2-methyl-1,4-naphthoquinone, lawsone, juglone, plumbagin,α-naphthoquinone, β-naphthoquinone and the like.

Among the aforementioned quinone compounds, preferred are o- andp-benzoquinones, α-naphthoquinone, β-naphthoquinone and lawsone.

The aforementioned quinone compound (B) can be used sinlgy, or incombination of two or more.

Condensation reaction

The condensation product of the aforementioned components (A) and (B),which is the indispensable constituent of the poller scale depositionpreventive agent according to the present invention, can be prepared byreacting the components (A) and (B) with each other in a suitablesolvent, optionally in the presence of a catalyst as required, normallyat a temperature of room temperature to 200° C. for 0.5 to 100 hours,and preferably at room temperature to 150° C. for 3 to 30 hours.

Since the component (B) acts also as a condensation catalyst, it isnormally unnecessary to add another condensation catalyst. However, thecondensation catalysts which may be additionally include, for example,elemental or molecular simple-substance halogens such as iodine,bromine, chlorine, fluorine and the like; oxo-acid and oxo-acid salts ofhalogen, such as iodic acid, periodic acid, potassium periodate, sodiumperchlorate and the like; inorganic peroxides such as hydrogen peroxide,sodium peroxide, potassium persulfate, ammonium persulfate and the like;organic peroxides such as peracetic acid, benzoyl peroxide, cumenhydroperoxide, perbenzoic acid, p-menthane hydroperoxide and the like;chlorides and sulfates of a metal selected from the group consisting ofiron and copper, such as ferrous chloride, ferric chloride, coppersulfate, cuprous chloride and the like; azo compounds such asα,α'-azobisisobutyronitrile, α,α'-azobis-2,4-dimethylvaleronitrile andthe like; aromatic nitro compounds such as nitrobenzene, o-, m- andp-oxynitrobenzenes, o-, m- and p-nitroanisoles, o-, m- andp-chloronitrobenzenes, o-, m- and p-nitrobenzoic acids, o-, m- andp-nitrobenzenesulfonic acids and the like; and so forth.

As a solvent for the condensation reaction, for example, organicsolvents such as alcohols, ketones, esters and the like can be used,among which it is preferable to use organic solvents miscible withwater. As the organic solvents miscible with water include, for example,alcohols such as methanol, ethanol, propanol and the like; ketones suchas acetone, methyl ethyl ketone and the like; esters such as methylacetate, ethyl acetate and the like; aprotic solvents such asdimethylformamide, dimethyl sulfoxide, acetonitrile and the like, amongwhich particularly preferred are alcohols. Further, mixed solvents ofwater and the aforementioned organic solvent miscible with water may bealso used.

The medium for performing the condensation reaction normally has a pH of1 to 13, and pH adjusters may be used without any particularrestrictions.

The relative amounts of the components (A) and (B) to be brought intothe condensation reaction are affected by kinds of the components (A)and (B) and solvent used, reaction temperature, reaction time and so on.Normally, it is preferable to use 0.01 to 10 parts by weight, morepreferably 0.1 to 5 parts by weight of the component (B), per part byweight of the component (A). If the amount of the component (B) is toolarge or too small, the resulting condensation product has a lowereffect in preventing polymer scale deposition. In addition, thecomponents (A) and (B) in the solvent during the condensation reactionhave a total concentration preferably in a range of 0.5 to 30% byweight, more preferably in a range of 1 to 15% by weight.

Polymer scale deposition preventive agent comprising an alkalinesolution containing the condensation product of the components (A) and(B)

The polymer scale deposition preventive agent according to the presentinvention comprises an alkaline solution containing the condensationproduct of the aforementioned components (A) and (B). Such a polymerscale deposition preventive agent is applied to inner wall surfaces,etc. of a polymerization vessel, and is dried to form a coating, wherebypolymer scale can be prevented from being deposited on thepolymerization vessel inner wall surfaces or the like.

The polymer scale deposition preventive agent is prepared, for example,such that the solution containing the condensation product obtained bythe aforementioned condensation reaction is optionally admixed with asolvent (which will be described below) as required, and the pH iscontrolled to the alkaline side. Alternatively, the polymer scaledeposition preventive agent may be prepared such that the aforementionedcondensation product-containing solution is introduced into cold waterto settle the condensation product, and then the sediment thus formed isseparated by filtration and dried, to which a solvent (described below)is added so as to control the pH to the alkaline side.

Because the polymer scale deposition preventive agent of the presentinvention is made alkaline, the solubility of the condensation productof the components (A) and (B) in the solvent is improved. Therefore, thepolymer scale deposition preventive agent is provided in a uniformsolution, so that when it is applied to the polymerization vessel innerwall surfaces, etc., an improved polymer scale deposition preventiveeffect can be obtained. Further, the polymer scale deposition preventiveagent of the present invention preferably has a pH of 7.5 to 13.5, morepreferably has a pH of 8.0 to 12.5. Alkaline compounds which may be usedfor pH adjustment include, for example, alkali metal compounds such asLiOH, NaOH, KOH, Na₂ CO₃, Na₂ HPO₄ and the like; ammonium compounds suchas NH₄ OH and the like; organic amine compounds such as ethylenediamine,monoethanolamine, diethanolamine, triethanolamine, and so forth.

As the solvent for use in preparation of the polymer scale depositionpreventive agent are exemplified, for example, water; alcohol solventssuch as methanol, ethanol, propanol, butanol, 2-butanol,2-methyl-1-propanol, 2-methyl-2-propanol, 3-methyl-1-butanol,2-methyl-2-butanol, 2-pentanol and the like; ketone solvents such asacetone, methyl ethyl ketone, methyl isobutyl ketone and the like; estersolvents such as methyl formate, ethyl formate, methyl acetate, ethylacetate, methyl acetoacetate and the like; ether solvents such as4-methyldioxolan, ethylene glycol diethyl ether and the like; furans;aprotic solvents such as dimethylformamide, dimethyl sulfoxide,acetonitrile and the like; and so forth. These solvents may be usedsingly, or as a mixed solvent of two or more on a case-by-case basis.

Among the above solvents, preferred are water and mixed solvents ofwater and an organic solvent miscible with water. As the organic solventmiscible with water among the aforementioned organic solvents areexemplified alcohol solvents such as methanol, ethanol, propanol and thelike; ketone solvents such as acetone, methyl ethyl ketone and the like;and ester solvents such as methyl acetate, ethyl acetate and the like.The mixed solvents of water and an organic solvent miscible with waterpreferably contain, when used, the organic solvent in such an amountthat there is no fear about inflammation, explosion or the like, andsafety in handling is ensured as to virulence, etc., specifically insuch an amount that the organic solvent is preferably not more than 50%by weight, more preferably not more than 30% by weight.

Other ingredients

Additionally, in order to further enhance the polymer scale depositionpreventive effect, it is preferable to add to the aforementionedpreventive agent at least one member selected from the group consistingof (C) a water-soluble polymeric compound, (D) an inorganic colloid and(E) an alkali metal silicate.

It is expected that these additives (C) to (E) presumably have actionsof interacting with the condensation product in such a manner as toimprove the hydrophilicity of the surfaces being coated (in the case ofthe water-soluble polymeric compound (C)) or to improve adhesion of thepolymer scale deposition preventive agent to the polymerization vesselinner wall (in the case of the inorganic colloid (D) and the alkalimetal silicate (E)).

(C) Water-soluble polymeric compound

As the water-soluble polymeric compound (C) are exemplified ampholyticpolymeric compounds such as gelatin, casein and the like; anionicpolymeric compounds such as polyacrylic acid, polystyrenesulfonic acid,carboxymethyl cellulose, alginic acid and the like; cationicnitrogen-containing polymeric compounds such as polyvinyl pyrrolidone,chitosan, polyacrylamide and the like; hydroxyl group-containingpolymeric compounds such as polyvinyl alcohol, hydroxyethyl cellulose,hydroxypropyl cellulose, pectin and the like; and so forth.

Among the aforementioned water-soluble polymeric is compounds, preferredare gelatin, casein, polyacrylic acid, carboxymethyl cellulose,polyvinyl pyrrolidone and pectin.

The water-soluble polymeric compounds (C) can be used singly, or incombination of two or more.

The component (C) is added in an amount of normally 1 to 1000 parts byweight, preferably 5 to 200 parts by weight, per 100 parts by weight ofthe condensation product of the components (A) and (B).

(D) Inorganic colloid

The inorganic colloids (D) are particulate colloids produced by acondensing method or a dispersing method using water as a dispersionmedium, with the colloidal particles ranging from 1 to 500 mμ in size.

Specifically as the inorganic colloids are exemplified colloids of anoxide and hydroxide of a metal selected from the group consisting ofaluminum, thorium, titanium, zirconium, antimony, tin, iron and thelike; colloids of tungstic acid, vanadium pentoxide, gold and silver;silver iodide sol; colloids of selenium, sulfur, silica and the like;and so forth.

Among the inorganic colloids (D), preferred are colloids of an oxide andhydroxide of aluminum, titanium, zirconium, tin and iron; and colloidalsilica.

The inorganic colloids (D) can be used alone as one species, or incombination of two or more species.

The component (C) is added in an amount of normally 1 to 1000 parts byweight, preferably 5 to 500 parts by weight, per 100 parts by weight ofthe aforementioned condensation product.

(E) Alkali metal silicates

As the alkali metal silicates (E) are exemplified metasilicates (M₂SiO₃), orthosilicates (M₄ SiO₄), disilicates (M₂ Si₂ O₃), trisilicates(M₃ Si₃ O₇), sesquisilicates (M₄ Si₃ O₁₀) and the like of alkali metalssuch as lithium, sodium, potassium and the like (wherein M stands for analkali metal such as lithium, sodium, potassium and the like); and waterglass.

The alkali metal silicates (E) can be used singly or in combination oftwo or more.

The component (E) is contained in an amount of normally 1 to 1000 partsby weight, preferably 5 to 500 parts by weighlt, per 100 parts by weightof the aforementioned condensation product.

Incidentally, where the component (D) and the component (E) are used incombination, the total amount of the components (D) and (E) ispreferably 1 to 1000 parts by weight, more preferably 5 to 500 parts byweight, per 100 parts by weight of the aforementioned condensationproduct.

For best improving the polymer scale deposition preventive effect, it ispreferable to use a combination of the water-soluble polymeric compound(C) with the inorganic colloid (D), or a combination of thewater-soluble polymeric compound (C) with the alkali metal silicate (E).Where the components (C) and (D) are used in combination, the component(D) is preferably used by 5 to 3000 parts by weight, and more preferablyused by 50 to 1000 parts by weight, per 100 parts by weight of thecomponent (C). Where the components (C) and (E) are used in combination,the component (E) is preferably used by 5 to 3000 parts by weight, andmore preferably used by 50 to 1000 parts by weight, per 100 parts byweight of the component (C).

The concentration of the condensation product in the aforementionedalkaline solution is not particularly limited, as long as the totalcoating weight described later can be obtained, which is normally on theorder of 0.001 to 5% by weight, preferably on the order of 0.01 to 1% byweight. In addition, where the components (C) to (E) are added, thetotal concentration of the aforementioned condensation product and thecomponents (C) to (E) is preferably on the order of 0.05 to 5% byweight, more preferably on the order of 0.1 to 2% by weight.

Formation of coating

To form a coating on inner wall surfaces of a polymerization vesselusing the polymer scale deposition preventive agent comprising thealkaline solution containing the condensation product of the components(A) and (B) prepared as described above, first the preventive agent isapplied to the inner wall surfaces of the polymerization vessel, whichis subsequently dried sufficiently at a temperature ranging, forexample, from room temperature to 100° C., followed by washing withwater as required.

Further, the aforementioned polymer scale deposition preventive agent ispreferably applied to not only the inner wall surfaces of apolymerization vessel but also other areas with which the monomer comesinto contact during polymerization. For example, there may beexemplified stirring blades, stirring shaft, baffles, condensers,headers, search coil, bolts, nuts, etc.

More preferably, it is recommended that the aforementioned polymer scaledeposition preventive agent may be subjected to formation of theaforementioned coating even at areas with which the monomer does notcome into contact during polymerization but on which polymer scale maybe likely deposited, for example, the inner surfaces, etc. of equipmentand pipes of an unreacted monomer recovery system. Specifically, theremay be exemplified the inner surfaces of monomer distillation columns,condensers, monomer stock tanks, valves, and so on.

Incidentally, the method of applying the polymer scale depositionpreventive agent to the inner wall surfaces of a polymerization vesselis not particularly restricted, for which, for example, it is possibleto use brush coating, spray coating, a method by filling thepolymerization vessel with the polymer scale deposition preventive agentfollowed by withdrawal thereof, as well as the automatic coating methodsas disclosed in Japanese Pre-examination Patent Publication (KOKAI) Nos.57-61001 and 55-36288, Japanese Patent Publication (KOHYO) Nos.56-501116 and 56-501117, and Japanese Pre-examination Patent Publication(KOKAI) No. 59-11303, etc.

Further, the method of drying wet coated surfaces provided byapplication of the polymer scale deposition preventive agent, is notrestricted, either. For example, the following methods can be used.Namely, there can be used a method in which, after the polymer scaledeposition preventive agent is applied, hot air with a suitable elevatedtemperature is blown to the coated surface; a method in which the innerwall surfaces of a polymerization vessel and the surfaces of other partsto be coated with the polymer scale deposition preventive agent arepreliminarily heated, for example, to a temperature of 30° to 80° C.,and the polymer scale deposition preventive agent is directly applied tothe heated surfaces; and so on. After coated surfaces are dried, thecoated surfaces are washed with water, if necessary.

The coating obtained in this manner has a total coating weight afterdried of normally 0.001 to 5 g/m², preferably 0.05 to 2 g/m².

The aforementioned coating operation may be performed every one to tenand several batches of polymerization. The formed coating has gooddurability and retains the polymer scale deposition-preventing action;therefore, the coating operation may not necessarily be carried outevery one batch of polymerization. Accordingly, productivity isimproved.

Polymerization

After the formation of the coating by applying the coating operationonto the inner wall surfaces of a polymerization vessel, and preferablyalso onto other areas with which monomer may come into contact duringpolymerization, etc. as described above, polymerization is carried outin the polymerization vessel in accordance with conventional procedures.That is, a monomer having an ethylenically unsaturated double bond and apolymerization initiator (catalyst) as well as optionally apolymerization medium such as water, etc., a dispersing agent such assuspending agents, solid dispersing agents, nonionic or anionicemulsifying agents, etc., and the like are charged, and thenpolymerization is carried out according to conventional procedures.

As the monomers having an ethylenically unsaturated double bond whichcan be polymerized by applying the process of the present invention areexemplified vinyl halides such as vinyl chloride and the like; vinylesters such as vinyl acetates, vinyl propionates and the like; acrylicacid, methacrylic acid, and their esters and salts; maleic acid, fumaricacid, and their esters and anhydrides; diene monomers such as butadiene,chloroprene, isoprene and the like; styrene; acrylonitrile; vinylidenehalides; vinyl ethers; and so forth. They may be used alone as onespecies, or in combination of two or more species.

Further, the process according to the present invention to be appliedhas no particular restriction on the type of polymerization, which iseffective in any of such polymerization types as suspensionpolymerization, emulsion polymerization, solution polymerization, bulkpolymerization, and gas phase polymerization, and is more suited topolymerization in an aqueous medium, such as suspension polymerization,emulsion polymerization and so forth.

In the following, taking the cases of suspension polymerization andemulsion polymerization as an example, general procedures ofpolymerization will be specifically described.

First, water and a dispersing agent are charged into a polymerizationvessel. Subsequently, the polymerization vessel is evacuated to reducethe internal pressure to 0.1 to 760 mmHg, and a monomer is then charged.At this time, the internal pressure of the polymerization vessel isusually 0.5 to 30 kgf/cm²· G. In addition, a polymerization initiator ischarged before charging and/or after charging the monomer. Subsequently,polymerization is carried out at a reaction temperature of 30° to 150°C. During the polymerization, one or more species of water, a dispersingagent and a polymerization initiator may be added, if necessary.Further, reaction temperature during the polymerization is differentdepending on the kind of monomer to be polymerized. For example, in thecase of polymerizing vinyl chloride, polymerization is carried out at30° to 80° C., while in the case of polymerizing styrene, polymerizationis carried out at 50° to 150° C. The polymerization may be judged to becompleted when the pressure inside the polymerization vessel has fallento 0 to 7 kgf/cm²· G, or when cooling water which is let flow into andout of a jacket provided around the outer circumference of thepolymerization vessel has come to show substantially no difference intemperature at an inlet and an outlet (i.e., when liberation of heat dueto polymerization reaction has disappeared). The amounts of water,dispersing agent and polymerization initiator to be charged forpolymerization are normally 20 to 500 parts by weight of water, 0.01 to30 parts by weight of the dispersing agent, and 0.01 to 5 parts byweight of the polymerization initiator, per 100 parts by weight of themonomer.

In solution polymerization, an organic solvent such as toluene, xylene,pyridine, etc. is used as the polymerization medium, in place of water.A dispersing agent may be used, if necessary. The other conditions forpolymerization are generally the same as those described for suspensionpolymerization and emulsion polymerization.

In bulk polymerization, after a polymerization vessel is evacuated to apressure of about 0.01 to 760 mmHg, a monomer and a polymerizationinitiator are charged into the polymerization vessel, and polymerizationis carried out at a reaction temperature of -10° to 250° C. For example,polymerization of vinyl chloride is carried out at 30°to 80° C., whilepolymerization of styrene is carried out at 50° to 150° C.

Where polymerization is carried out by applying the process of thepresent invention, it is possible to prevent polymer scale from beingdeposited, regardless of the materials of the inner wall surfaces, etc.of a polymerization vessel. For example, the polymer scale depositioncan be prevented from occurring during polymerization in apolymerization vessel treated with glass-lining or the like as a matterof course, as well as a polymerization vessel made of stainless steel orother steel and so forth.

Further, those added to polymerization systems can be used without anylimitation. That is to say, the process of the present invention caneffectively prevent polymer scale deposition in polymerization systemsincluding, for example, polymerization initiators such as t-butylperoxyneodecanoate, bis(2-ethylhexyl) peroxydicarbonate,3,5,5-trimethylhexanoyl peroxide, α-cumyl peroxyneodecanoate, cumenehydroperoxide, cyclohexanone peroxide, t-butyl peroxypivalate,bis(2-ethoxyethyl) peroxydicarbonate, benzoyl peroxide, lauroylperoxide, 2,4-dichlorobenzoyl peroxide, diisopropyl peroxydicarbonate,α,α'-azobisisobutyronitrile, α,α'-azobis-2,4-dimethylvaleronitrile,potassium peroxodisulfate, ammonium peroxodisulfate, p-menthanehydroperoxide, etc.; suspending agents comprised of, for example,natural or synthetic polymeric compounds such as partially saponifiedpolyvinyl alcohols, polyacrylic acids, vinyl acetate/maleic anhydridecopolymers, cellulose derivatives (e.g. hydroxypropyl methyl cellulose),gelatin, etc.; solid dispersing agents such as calcium phosphate,hydroxyapatite, etc.; nonionic emulsifying agents such as sorbitanmonolaurate, sorbitan trioleate, polyoxyethylene alkyl ether, etc.;anionic emulsifying agents such as sodium lauryl sulfate, sodiumalkylbenzenesulfonates (e.g. sodium dodecylbenzenesulfonate), sodiumdioctylsulfosuccinate, etc.; fillers such as calcium carbonate, titaniumoxide, etc.; stabilizers such as tribasic lead sulfate, calciumstearate, dibutyltin dilaurate, dioctyltin mercaptide, etc.; lubricantssuch as rice wax, stearic acid, cetyl alcohol, etc.; plasticizers suchas DOP, DBP, etc.; chain transfer agents such as mercaptans (e.g.t-dodecyl mercaptan), trichloroethylene, etc.; pH adjusters, and soforth.

Incidentally, in addition to being used for formation of the coating onthe inner wall surfaces etc. of the polymerization vessel, the polymerscale deposition preventive agent of the present invention may furtherbe added directly to the polymerization system, whereby it is alsopossible to enhance the effect in preventing deposition of polymerscale. In that case, the addition amount of the polymer scale depositionpreventive agent suitably ranges from about 10 to about 1000 ppm basedon the total weight of the monomer or monomers to be charged. At thetime of the addition, care should be taken not to affect adversely thefish eye, bulk specific gravity, particle size distribution or otherqualities of the resulting polymeric product.

EXAMPLES

The present invention will now be described in detail below, withreference to working examples thereof and comparative examples.Incidentally, in each of the tables below, the experiments bearing a No.marked with * are comparative examples, and the other experiments,bearing a non-marked No., are working examples of the present invention.

Preparation Example 1

Preparation of condensation product No. 1

A reaction vessel having an internal capacity of 2 liters equipped witha reflex condenser was charged with 800 g of methanol, 100 g ofdimethylformamide (DMF) and 40 g of 4,4'-diaminodiphenylsulfone ascomponent (A), followed by stirring at room temperature to dissolve4,4'-diaminodiphenylsulfone in methanol/DMF.

To the methanol/DMF solution thus obtained was added 60 g ofα-naphthoquinone as component (B) to raise the temperature to 65° C. toperform reaction at 65° C. for 24 hours. Subsequently, an obtainedreaction mixture was cooled, and added dropwise to water, and adeposited sediment was separated by filtration and dried. Thus acondensation product No. 1 was obtained.

Preparation of condensation products Nos. 2 to 7

In each preparation, a condensation product was prepared in the samemanner as in the preparation of the condensation product No. 1 exceptfor using the component (A) (diphenyl compound having at least two aminogroups) and the component (B) (quinone compound) shown in Table 1, andthe solvent shown in Table 2.

Total concentration of (A)+(B) , weight ratio of (A):(B), reactiontemperature and reaction time are set forth in Table 2.

                  TABLE 1                                                         ______________________________________                                        Condensation                                                                           (A)               (B)                                                product  Diphenyl compound having                                                                        Quinone                                            No.      at least two amino groups                                                                       compound                                           ______________________________________                                        1        4,4'-Diaminodiphenylsulfone                                                                     α-Naphthoquinone                              2*      4,4'-Diaminodiphenylsulfone                                                                       --                                               Naphthoquinone             α                                            4        4,4'-Diaminobenzanilide                                                                         α-Naphthoquinone                             5        4,4'-Diaminodiphenyl ether                                                                      p-Benzoquinone                                     6        4,4'-Diaminodiphenylmethane                                                                     p-Benzoquinone                                     7        4,4'-Diaminodiphenyl sulfide                                                                    p-Benzoquinone                                     ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Conden-                                                                              Total conc.               Reaction                                     sation of        (A):(B)         tempera-                                                                             Reaction                              product                                                                              (A) + (B) (wt.    Solvent ture   time                                  No.    (%)       ratio)  (wt. ratio)                                                                           (°C.)                                                                         (hour)                                ______________________________________                                        1      10        1:1.5   Methanol/                                                                             65     24                                                             DMF (8:1)                                             2*    10        --      Methanol/                                                                             65     24                                                             DMF (8:1)                                             3*    10        --      Methanol/                                                                             65     24                                                             DMF (8:1)                                            4      10        1:2     Methanol                                                                              65     24                                    5      10        1:1.5   Methanol/                                                                             65     24                                                             DMSO                                                                          (8:2)                                                6      10        1:0.5   Methanol/                                                                             65     48                                                             Aceto-                                                                        nitrile (8:2)                                        7       5        1:1     Methanol/                                                                             65     24                                                             DMF (8:2)                                            ______________________________________                                         DMF: Dimethylformamide                                                        DMSO: Dimethyl sulfoxide                                                 

Example 1 (Experiment Nos. 101 to 108)

In each experiment, a stainless-steel polymerization vessel having aninternal capacity of 1000 liters and equipped with a stirrer was used asthe polymerization vessel.

In each experiment, a polymer scale deposition preventive agent wasprepared by using the condensation product (F), water-soluble polymericcompound (C), inorganic colloid (D) and alkali metal silicate (E) setforth in Table 3, and alkaline compound and solvent set forth in Table 4so as to provide conditions (solvent composition, total concentration ofcondensation product (F)+(C)+(D)+(E), weight ratio of (F):(C):(D):(E),and pH) shown in Table 4. Incidentally, the inorganic colloids as thecomponent (D) (a to g, in Table 3 and Table 7) used in this example andExample 2 described below are shown in Table 6.

In each experiment, the polymer scale deposition preventive agentprepared as above was applied to the inner wall of the polymerizationvessel and to the stirring shaft, stirring blades and the like partswith which the monomer might come into contact during polymerization, toperform heating and drying at 40° C. for 15 minutes to form a coating,followed by washing the inside of the polymerization vessel with water.

Subsequently, in each experiment, polymerization was conducted asfollows. The polymerization vessel provided with the coating by thecoating treatment as above was charged with 400 kg of water, 200 kg ofvinyl chloride, 250 g of partially saponified polyvinyl alcohol, 25 g ofhydroxypropyl methyl cellulose and 70 g of 3,5,5-trimethylhexanoylperoxide, followed by polymerization with stirring at 66° C. for 6hours. After the polymerization was finished, the polymeric product andunreacted monomer were recovered, and the inside of the polymerizationvessel was washed with water to remove residual resin.

Thereafter, the above process including the polymerization and thewashing of the inside of polymerization vessel with water was regardedas one batch, and the same process was repeated by the repetition numberof batches being given in Table 5, without carrying out the coatingoperation.

For each experiment, after the final batch was over, the amount ofpolymer scale deposited on areas located in the liquid-phase region andthat on areas around the interface between gas and liquid phases insidethe polymerization vessel were determined according to the methoddescribed below. The results are given in Table 5.

Measurement of the amount of polymer scale deposited

The scale deposited in an area of 10 cm square at a predeterminedlocation on the inner wall of a polymerization vessel was scraped offwith a stainless steel spatula as completely as can be confirmed withthe naked eye, and then weighed on a balance. The measured value wasmultiplied by 100 to obtain the amount of the deposited polymer scaleper area of 1 m².

Besides, the number of fish eyes appearing upon formation of a polymerobtained in each experiment into a sheet was measured according to themethod below. The results are given in Table 5.

Measurement of fish eyes

A mixture, which was prepared in a blending ratio of 100 parts by weightof a polymer obtained, 50 parts by weight of dioctyl phthalate (DOP), 1part by weight of dibutyltin dilaurate, 1 part by weight of cetylalcohol, 0.25 part by weight of titanium oxide and 0.05 part by weightof carbon black, was kneaded at 150° C. for 7 minutes with 6 inch rolls,and then formed into a sheet 0.2 mm thick. The obtained sheet wasexamined for the number of fish eyes contained per 100 cm² by means ofthe light transmission method.

Further, in order to evaluate initial coloration in the case offormation of the polymer obtained in each experiment into a sheet,measurement of luminosity index (L value) was carried out according tothe method below. The results are given in Table 5.

Measurement of luminosity index (L value)

A hundred (100) parts by weight of the obtained polymer, 1 part byweight of a tin laurate stabilizing agent (TS-101, product of AkishimaChemical Co.), 0.5 part by weight of cadmium stabilizing agent (C-100J,product of Katsuta Kako Co.), and 50 parts by weight of dioctylphthalate as a plasticizer were kneaded at 160° C. for 5 minutes with atwin roll mill, and then formed into a sheet 1 mm thick. Subsequently,the formed sheet was placed in a mold measuring 4×4×1.5 cm, heated at160° C. under a pressure of 65 to 70 kgf/cm² for 0.2 hour, and pressmolded to prepare a test specimen. This test specimen was measured forluminosity index L in the Hunter's color difference equation describedin JIS Z 8730 (1980). The greater the value of L, the higher thewhiteness evaluated, namely, the better the initial colorationevaluated.

The value of L was determined as follows.

The stimulus value Y of XYZ color system was determined by thephotoelectric tristimulus colorimetry using the standard light C andphotoelectric colorimeter (Color measuring color difference meter ModelZ-1001 DP, product of Nippon Denshoku Kogyo K.K.) in accordance withdescription of JIS Z 8722. As the geometric condition of illuminationand light reception, the condition d defined in section 4.3.1 of JIS Z8722 was adopted. From the stimulus value Y obtained, the L value wascalculated based on the equation: L=10Y^(1/2) described in JIS Z 8730(1980).

                  TABLE 3                                                         ______________________________________                                              (F)        (C)                   (E)                                          Condensation                                                                             Water-soluble  (D)    Alkali                                 Exp.  product    polymeric      Inorganic                                                                            metal                                  No.   No.        compound       colloid                                                                              silicate                               ______________________________________                                        101   1          Gelatin        b      --                                     102*   2*        Gelatin        b      --                                     103*   3*        Gelatin        b      --                                     104   4          Polyacrylic acid                                                                             c      --                                     105   5          Polyvinyl alcohol                                                                            a      --                                     106   6          --             --     --                                     107*  7          Polyvinyl pyrrolidone                                                                        d      --                                     108   7          Polyvinyl pyrrolidone                                                                        --     water                                                                         glass                                  ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                             Total conc.                                                                   of (F) +              Alkaline                                                (C) +                 com-                                               Exp. (D) + (E) (F):(C):(D):(E)                                                                           pound  Solvent                                     No.  (wt. %)   (weight ratio)                                                                            (pH)   (weight ratio)                              ______________________________________                                        101  0.5       100:100:100:0                                                                             NaOH   Water:Methanol                                                         (11.0) (70:30)                                     102* 0.5       100:100:100:0                                                                             NaOH   Water:Methanol                                                         (11.0) (70:30)                                     103* 0.5       100:100:100:0                                                                             NaOH   Water:Methanol                                                         (11.0) (70:30)                                     104  0.5       100:50:100:0                                                                              NaOH   Water:Methanol                                                         (11.0) (90:10)                                     105  0.5       100:50:200:0                                                                              KOH    Water:Methanol                                                         (11.0) (90:10)                                     106  0.3         --        Ethy-  Water:Methanol                                                         lene-  (90:10)                                                                diamine                                                                       (11.0)                                             107* 0.3       100:100:200:0                                                                              --    Water:Methanol                                                                (90:10)                                     108  0.3       100:100:0:300                                                                             NaOH   Water:Methanol                                                         (12.0) (90:10)                                     ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                                 Results of polymerization                                                       Scale deposition                                                   Repetition amount (g/m.sup.2)                                                                           Number                                                   number            Gas phase-                                                                             of     Luminosity                             Exp. of        Liquid  liquid phase                                                                           fish   index                                  No.  batch     phase   interface                                                                              eyes   (L)                                    ______________________________________                                        101  4         0        3        9     73.0                                   102* 2         20      90       24     73.0                                   103* 2         20      93       28     73.0                                   104  5         0        4        8     73.0                                   105  4         0        3        8     73.0                                   106  3         0       12       16     73.0                                   107* 2         18      88       25     73.0                                   108  4         0        4        8     73.0                                   ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                               Diameter of                                                            Inorganic                                                                            colloidal                                                              colloid                                                                              particles   Name of article                                                                             Manufacturer                                 ______________________________________                                        a      10-20    mμ  Snowtex O*  Nissan                                                            (colloidal silica)                                                                        Chemical                                                                      Industries. Ltd.                           b      5-7      mμ  Snowtex CXS-9*                                                                            Nissan                                                            (colloidal silica)                                                                        Chemical                                                                      Industries. Ltd.                           c      100-200  mμ  Titanium oxide                                                                            Nissan                                                                        Chemical                                                                      Industries. Ltd.                           d      10-20    mμ  Aluminum oxide                                                                            Nissan                                                                        Chemical                                                                      Industries. Ltd.                           e      60-70    mμ  Zirconium oxide                                                                           Nissan                                                                        Chemical                                                                      Industries. Ltd.                           f      20-50    mμ  Tin oxide   Nissan                                                                        Chemical                                                                      Industries. Ltd.                           g      10-15    mμ  Iron hydroxide                                                                            produced by the                                                               present                                                                       inventors                                  ______________________________________                                         Note                                                                          *Trade name                                                              

In each experiment, a stainless-steel polymerization vessel having aninternal capacity of 20 liters and equipped with a stirrer was used asthe polymerization vessel.

In each experiment, a polymer scale deposition preventive agent wasprepared by using the condensation product (F), water-soluble polymericcompound (C), inorganic colloid (D) and alkali metal silicate (m) setforth in Table 7, and alkaline compound and solvent set forth in Table 8so as to provide conditions (solvent composition, total concentration ofcondensation product (F)+(C)+(D)+(E), weight ratio of (F):(C):(D):(E),and pH) shown in Table 8. Each of these polymer scale depositionpreventive agents was applied to the inner wall of the polymerizationvessel and to the stirring shaft, stirring blades and the like partswith which the monomer might come into contact during polymerization, toperform heating and drying at 40° C. for 15 minutes to form a coating,followed by washing the inside of the polymerization vessel with water.

Subsequently, in each experiment, polymerization was conducted asfollows. The polymerization vessel provided with the coating by thecoating treatment as above was charged with 9 kg of water, 225 g ofsodium dodecylbenzenesulfonate, 12 g of t-dodecyl mercaptan and 13 g ofpotassium peroxodisulfate. The inside atmosphere of the polymerizationvessel was replaced with nitrogen gas, thereafter 1.3 kg of styrene and3.8 kg of butadiene were charged to carry out polymerization at 50° C.for 20 hours. After the polymerization was finished, the polymericproduct and unreacted monomer were recovered, and the inside of thepolymerization vessel was washed with water to remove residual resin.

Thereafter, the above process including the polymerization and thewashing of the inside of polymerization vessel with water was regardedas one batch, and the same process was repeated by the repetition numberof batches being given in Table 9, without carrying out the coatingoperation.

For each experiment, after the final batch was over, the amount ofpolymer scale deposited on areas located in the liquid-phase region andthat on areas around the interface between gas and liquid phases insidethe polymerization vessel were determined according to the same methodas in Example 1. The results are given in Table 9.

In addition, in order to evaluate initial coloration in the case offormation of the polymer obtained in each experiment into a sheet,measurement of luminosity index (L value) was carried out according tothe method below. The results are given in Table 9.

Measurement of luminosity index (L value)

To 1 kg of the polymer latex obtained was added 1 kg of 2% magnesiumsulfate solution to cause aggregation and sedimentation, and thereafterthe sediment was filtered off. The filtered sediment was washed with hotwater at 80° to 90° C. twice or three times, and then dried at 40° C.for 25 hours in a vacuum dryer to obtain a resin.

The obtained resin was placed in a mold measuring 9×9×0.1 cm (depth),heated at 195° C. under a pressure of 50 to 60 kgf/cm² for 0.2 hour, andpress molded under a final pressure of 80 kgf/cm² to prepare a testspecimen. This test specimen was measured for luminosity index L in thesame manner as in Example 1.

                  TABLE 7                                                         ______________________________________                                              (F)        (C)                   (E)                                          Condensation                                                                             Water-soluble  (D)    Alkali                                 Exp.  product    polymeric      Inorganic                                                                            metal                                  No.   No.        compound       colloid                                                                              silicate                               ______________________________________                                        201   1          Polyacrylic acid                                                                             b      --                                     202*   2*        Polyacrylic acid                                                                             b      --                                     203*   3*        Polyacrylic acid                                                                             b      --                                     204   4          Sodium alginate                                                                              e      --                                     205   5          Polyvinyl pyrrolidone                                                                        f      --                                     206   6          --             --     --                                     207   7          Gelatin        g      --                                     ______________________________________                                    

                  TABLE 8                                                         ______________________________________                                             Total conc.                                                                   of (F) +              Alkaline                                                (C) +                 com-                                               Exp. (D) + (E) (F):(C):(D):(E)                                                                           pound  Solvent                                     No.  (wt. %)   (weight ratio)                                                                            (pH)   (weight ratio)                              ______________________________________                                        201  0.5       100:100:100:0                                                                             NaOH   Water:Methanol                                                         (11.5) (70:30)                                     202* 0.5       100:100:100:0                                                                             NaOH   Water:Methanol                                                         (11.5) (70:30)                                     203* 0.5       100:100:100:0                                                                             NaOH   Water:Methanol                                                         (11.5) (70:30)                                     204  0.5       100:100:200:0                                                                             NaOH   Water:Methanol                                                         (11.5) (70:30)                                     205  0.5       100:100:300:0                                                                             NaOH   Water:Methanol                                                         (11.5) (70:30)                                     206  0.5         --        Ethy-  Water:Methanol                                                         lene-  (70:30)                                                                diamine                                                                       (11.0)                                             207  0.5       100:50:100:0                                                                              Ethy-  Water:Methanol                                                         lene-  (70:30)                                                                diamine                                                                       (11.0)                                             ______________________________________                                    

                  TABLE 9                                                         ______________________________________                                        Repetition  Results of polymerization                                         number      Scale deposition amount (g/m.sup.2)                                                              Luminosity                                     Exp.  of        Liquid  Gas phase-liquid phase                                                                     index                                    No.   batch     phase   interface    (L)                                      ______________________________________                                        201   2         0       3            85.0                                     202*  1         16      155          85.0                                     203*  1         21      165          85.0                                     204   2         0       2            85.0                                     205   2         0       1            85.0                                     206   1         0       2            85.0                                     207   2         0       2            85.0                                     ______________________________________                                    

Example 3

A stainless-steel polymerization vessel having an internal capacity of20 liters and equipped with a stirrer was used as the polymerizationvessel.

The polymer scale deposition preventive agent used in the experiment No.201 of Example 2 was applied to the inner wall of the polymerizationvessel and to the stirring shaft, stirring blades and the like partswith which the monomer might come into contact during polymerization, toperform heating and drying at 50° C. for 15 minutes to form a coating,followed by washing with water.

Thereafter, the polymerization vessel provided with the coating by thecoating treatment as above was charged with 4.0 kg of water and 6 g ofsodium dodecylbenzenesulfonate, and temperature was raised to 60° C.with stirring. Subsequently after the gas phase in the polymerizationvessel was replaced with nitrogen gas, 94 g of n-butyl acrylate, 220 gof methyl methacrylate, 5 g of acrylic acid and 5 g of methacrylic acidwere charged, and subsequently 1 g of ammonium persulfate and 1 g ofsodium hydrosulfite were charged to perform stirring at 60° C. for 20minutes.

Furthermore, into the aforementioned polymerization vessel were added amonomeric mixture (prepared by mixing 2.1 kg of n-butyl acrylate, 4.8 kgof methyl methacrylate, 100 g of acrylic acid and 100 g of methacrylicacid), 500 g of an aqueous 1 wt. % ammonium persulfate solution, 500 gof an aqueous 1 wt. % sodium hydrosulfite solution and 2.0 kg of anaqueous 25 wt. % polyoxyethylene nonyl phenyl ether solutionrespectively evenly over a 3-hour period. After the addition wascompleted, the aforementioned polymerization vessel was subjected totemperature raising to 70° C. to perform polymerization for 2 hours.

After the polymerization was over, the resulting polymeric product andunreacted monomers were recovered, and the inside of the polymerizationvessel was washed with water to remove residual resin.

Thereafter, the operation from the formation of the coating throughpolymerization to the washing of the inside of the polymerization vesselwith water as described above was regarded as one batch, which wasrepeated 80 batches, and the amount of polymer scale deposited on areaslocalted in the liquid-phase region and that on areas around theinterface between gas and liquid phases inside the polymerization vesselupon the 80th batch were measured in the same manner as in Example 1. Asa result, the amount of polymer scale deposited on areas located in theliquid-phase region was 0 g/m², and the amount of polymer scaledeposited on areas around the interface between gas and liquid phaseswas 20 g/m².

We claim:
 1. A polymer scale deposition preventive agent for use inpolymerization of a monomer having an ethylenically unsaturated doublebond, comprising an alkaline solution having as a solvent thereof wateror a mixed solvent of water and an organic solvent miscible with water,the amount of water contained in the mixed solvent being more than 70%by weight, and said alkaline solution having a pH of 7.5 to 13.5 whichhas been adjusted by the addition of an alkaline compound, andcontaining a condensation product of:(A) a diphenyl compound having atleast two amino groups represented by the following general formula (1):##STR5## wherein a plurality of R¹ 's may be the same or different,which are --H, --OH, --COOH, -SO₃ H, --NH₂, --Cl, --NO₂, --COCH₃,--OCH₃, --N(CH₃)₂ or an alkyl group having 1 to 3 carbon atoms, whereinX is an alkylene group having 1 to 5 carbon atoms, --N(CH₃)--, --C(CH₃)₂--, --CONH--, --P(═O)H--, --SO₂ --, --O--, --S--, or --Si(R)₂ --, whereR is an alkyl group having 1-10 carbon atoms, and wherein n is aninteger of 1 or 2; and (B) a quinone compound.
 2. The polymer scaledeposition preventive agent according to claim 1, wherein said component(A) contains at least one compound selected from the group consisting of4,4'-diaminodiphenylsulfone, 4,4'-diaminobenzanilide,4,4'-diaminodiphenyl ether and 4,4'-diaminodiphenylmethane.
 3. Thepolymer scale deposition preventive agent according to claim 1, whereinsaid component (B) comprises a compound selected from the groupconsisting of the compounds represented by the following generalformulae (2) to (5):a compound represented by: ##STR6## wherein aplurality of R² 's may be the same or different, which are --H, --NH₂,--Cl, --Br, --OH, --NO₂, --COCH₃, --OCH₃, --N(CH₃)₂, --COOH, --SO₃ H, oran alkyl group having 1 to 3 carbon atoms; a compound represented by:##STR7## wherein a plurality of R² 's may be the same or different,which are as defined above; a compound represented by: ##STR8## whereina plurality of R² 's may be the same or different, which are as definedabove, and wherein a plurality of R³ 's may be the same or different,which are --H, --Cl, --Br, --OH, --COCH₃, --OCH₃, --CH₃, --COOH or --SO₃H; and a compound represented by: ##STR9## wherein a plurality of R² 'smay be the same or different, which are as defined above, and wherein aplurality of R³ 's may be the same or different, which are as definedabove.
 4. The polymer scale deposition preventive agent according toclaim 1, wherein said component (B) comprises at least one compoundselected from the group consisting of o- and p-benzoquinones,α-naphthoquinone, β-naphthoquinone and lawsone.
 5. The polymer scaledeposition preventive agent according to claim 1, wherein saidcondensation product has been produced by condensation of 0.01 to 10parts by weight of the component (B) with 1 part by weight of thecomponent (A).
 6. The polymer scale deposition preventive agentaccording to claim 1, further comprising at least one member selectedfrom the group consisting of:(C) a water-soluble polymeric compound; (D)an inorganic colloid; and (E) an alkali metal silicate.
 7. The polymerscale deposition preventive agent, according to claim 1, wherein saidalkaline compound is selected from the group consisting of LiOH, NaOH,KOH, Na₂ CO₃, Na₂ HPO₄, NH₄ OH, ethylenediamine, monoethanolamine,diethanolamine and triethanolamine.
 8. The polymer scale depositionpreventive agent according to claim 1, wherein the alkaline solution hasa pH of 8.0 to 12.5.
 9. The polymer scale deposition preventive agentaccording to claim 1, wherein the condensation product has been producedby reacting the components (A) and (B) at room temperature to 150° C.for 3 to 30 hours.